Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.47	6.270%	$223.6665	$223.67	$223.65	$223.70
Purchase #2	$80.80	8.573%	$87.727	$87.73	$87.75	$87.70
Purchase #3	$76.51	6.300%	$81.3301	$81.33	$81.35	$81.30
Purchase #4	$56.97	4.684%	$59.6385	$59.64	$59.65	$59.60
Purchase #5	$34.83	4.198%	$36.2922	$36.29	$36.30	$36.30
Purchase #6	$36.48	9.358%	$39.8938	$39.89	$39.90	$39.90
Purchase #7	$157.48	8.779%	$171.3052	$171.31	$171.30	$171.30
7 purchase totals =	$653.54		$699.8533	$699.86	$699.90	$699.80